The health and well-being of our flock is always important, but never more so than during gestation, beginning during breeding in the fall and extending to nearly April 1 when our last ewes deliver their lambs. Each ewe is pregnant for about 150 days, and toward the end she can carry up to about 45 pounds of lambs plus lots of fluid and other supporting tissues. It is amazing how much some of these ewes carry!
During this period, the nutrition our ewes receive is reflected not only in the health of the ewes but also in the lambs they eventually produce. I’m sure you’ve heard the saying “You are what you eat.” Well, our sheep are also a reflection of what they eat and the nutrition they get through the year, particularly during gestation.
The first trimester—during the tail end of breeding and the period just after—is an important time for good nutrition because this is the time when all of the support structures for the pregnancy are composed. Good nutrition means good placental growth, and it also makes sure the needed building blocks are present for those early systems to form (including brain growth and the rest of the central nervous system, for example). The ewes don’t need much more than their maintenance ration – but this is not a time to reduce their intake or to feed poor-quality hay. We usually let them continue to graze our fields while we provide high-quality hay in the barns. That way, as the pastures drop in nutrition after the ground freezes, the ewes have another source of feed available.
The second trimester brings much differentiation in the cells of the fetus, and the various body systems are formed. By the beginning of the second trimester, most of the primary wool follicles are in place – these are the coarser fleece fibers. The groundwork for the lateral and secondary follicles is laid between days 60 and 100, encompassing most of the second trimester. This means that poor nutrition during this time can reduce the number of follicles that will produce finer fibers, resulting in less wool and coarser wool for the lifetime of the sheep. In order for a sheep to produce the quantity and quality of wool that it is genetically programmed to produce, all of these genetically programmed follicles must be present – and that means good nutrition is essential during this critical time, as well as in the months after birth when these follicles mature.
Seventy percent of fetal growth occurs in the last trimester, from days 100-150. If the ewe is carrying large twins or triplets (or more!), her rumen or fermentation stomach takes up less and less space as her lambs rapidly grow. The bottom line is that she can no longer eat enough hay to meet her own needs and those of her lambs, so this is the time to consider more nutrient-rich feeds like a grain blend. If a ewe begins to burn her own internal fat in order to supply the needed calories, she can develop pregnancy toxemia (ketosis), which often results in a bad outcome for both the ewe and her lambs.
As part of our feeding regimen, we provide our high-nutrition group (those ewe lambs who are bred and those adults carrying triplets or more) with alfalfa hay during the last half of their pregnancies and a high-energy grain blend during the last trimester. At the start of every new year, we put out a protein block (18% protein), allowing free access until their lambs are weaned in late spring. Yesterday I put one of those blocks out for the high-nutrition group, and the crush of sheep to get to it was unbelievable!
I know from experience that the ewes really like the protein block, but this year’s reaction surprised me a bit. Not only did the ewes crowd around the block, but they were crawling over each other as they tried to get to it, something that hasn’t been quite so obvious before. As I thought about it, I suspected that it might be due to the fact that this year our first one-third or so of the alfalfa hay is a mixed grass/alfalfa blend rather than straight alfalfa. We use alfalfa because it is higher in protein, so this year’s bales to date have been lower in protein than our usual ration at this time of year. We are just about to start in on the pure alfalfa bales for the rest of the season.
I can’t help but wonder whether this year’s crush to get to the protein block reflects the lower protein levels they have gotten so far in their hay and their desire to raise those levels via the block. I don’t know. What I do know is that the ewes in the high-nutrition group spent about an hour yesterday eating bits off the block in two tiers: the bigger adult ewes carrying three or four fetuses ate standing while the bred ewe lambs (soon to be yearlings) crawled under them and ate from between their legs. I’m not sure how long this two-tier system lasted, but I checked back a couple of times, so it went on for a while! Thankfully, by today the crush has ended and things seem to be back to normal!
Happy New Year!